1. Field of the Invention
The present invention relates to an image forming method of transferring plural toner images, formed on a plurality of image bearing members, in a superposed manner onto a recording material, and more particularly to an image forming method capable of correcting a relative positional relationship of such toner images on the image bearing members.
2. Related Background Art
In such an image forming apparatus, toner images are formed on first and second image bearing members. Subsequently, the first toner image on the first image bearing member and the second toner image on the second image bearing member are transferred in a superposed manner onto the recording material. Finally, the first and second toner images are heated and fixed on the recording material. In the course of a continuous printing job of executing image formations in a consecutive manner, the relative positional relationship of the first toner image and the second toner image is corrected to reduce an error in the mutually superposed toner images. Such correction of the mutual position is executed, based on a result of detections of alignment marks formed on the first image bearing member and the second image bearing member.
However, in case the image is formed, in a continuous printing job, on a recording sheet having a short width in a direction perpendicular to a transport direction (such direction being hereinafter called a thrust direction), such error cannot be reduced sufficiently. More specifically, in case of forming an image on a recording sheet having a short length in the width direction, a sheet non-passing area is formed on an end portion of the fixing member, and the heat in such a sheet non-passing area is released inside the apparatus, resulting in an elevated temperature in the apparatus and causing a deformation thereof, thus aggravating the error.